The invention relates generally to the field of curable compositions for forming a refractory material, as well as the refractory material itself, as used for example in ovens or grills. In particular, the invention relates to the field of such compositions where the resulting hardened material is comprised of crushed pumice, calcium aluminate cement and glass fibers.
For ultra-high temperature applications, special materials which can withstand the extreme temperatures without rapid deterioration must be used. Many such materials are known in the industry. For example, it is well known to use refractory blocks or bricks in industrial ovens. These materials have both high temperature resistance and high strength.
Pumice is a volcanic stone which is strong yet lightweight. A cubic foot can weigh as little as 24 to 30 pounds, due to the presence of numerous sealed air chambers and pockets within the individual stones. Crushed pumice can range in size from pieces three-quarter inches in diameter to that of a grain of sand. Pumice will actually float in water. Prior to this invention, the pumice has always been mixed with portland cement and formed into blocks, panels or bricks, usually for structural applications. Portland cement is an hydraulic cement produced by pulverizing clinker consisting essentially of hydraulic calcium silicates, usually containing one or more forms of calcium sulfate as an interground addition. The pumice allows for a block roughly one-third lighter in weight than a block of conventional concrete. The pumice block has good insulation properties due to the entrapped air chambers, but is not suitable for extreme temperature applications because the portland cement will degrade as high temperatures.
It has been discovered that pumice panels or blocks having improved temperature insulation, radiation and diffusion properties can be formed of a new composition not known in the field, where portland cement is replaced by calcium aluminate cement. The pumice panels or blocks are particularly applicable for use as liners in high temperature ovens or grills, such as are used in industry for curing or cooking. The presence of the pumice containing panels or blocks significantly increases the efficiency of the ovens and grills, resulting in savings in fuel consumption and processing time.